Transcript for Cold conditions affecting Thanksgiving travel
And it is slow going across much of this country. The Thanksgiving storms already on the move. More than 100 million Americans in 32 states under alerts tonight. The first storm, deadly already. Whiteout conditions at the Denver airport, stranding travelers. Grounding hundreds of flights. A deadly pie yul shutting down I-70 for a time. And treacherous conditions on I-80 in Nebraska, sending this van skidding off the road. Countless accidents across several stays tonight. The storm moving through the midwest, then right into the east with millions set to travel tomorrow and potentially dangerous winds on Thanksgiving day. And then there is another major system that will sweep through afterward, just in time for so many as they then travel home after Thanksgiving. So, we time it all out for you tonight. ABC's Clayton Sandell leading us off from Aurora, Colorado. Reporter: Tonight, drivers packing for Thanksgiving trips are finding highways packed with treacherous snow and ice. This van trying to pass a snowplow lost control on I-80 in Nebraska, spinning into the median. This semi overturned near grand island. On interstate 70 west of Denver, a snowy mountain crash claiming at least one life. Not far away, a rockslide closed part of the major highway for hours. On Colorado's eastern plains, whiteout blizzard conditions brought another I-70 shutdown. Woke up and thought I'd take a chance. But no dice. It's just too dicey. Thank god they closed the roads. Reporter: Nearly a foot of snow dumped into the Denver area. Motorists fighting losing battles against spinning tires, some giving up, driving the wrong way to escape. Firefighters race to keep up with countless crashes. Luckily, no one hurt in this collision. And in Colorado Springs -- Apparently, there's just snow all over the place. Nobody's going anywhere. Reporter: Back at the Denver airport, an urgent effort to clear runways. Nearly 550 con selled flights since Monday, and an overnight stay for more than 1,is 00 stranded travelers. ABC's Alex Perez is ahead of the storm in Minneapolis. With this storm on the move, here in Minneapolis, officials are bracing for more delays and cancellations. Crews will be out all night, clearing runways. Nearly 3348 million passengers will fly on Wednesday alone. Reporter: A second storm, now slamming Oregon with hurricane-force wind gusts and heavy snow. And David, this is one of the lingering travel nightmares. A few cars are sneaking through, be officially, interstate 70 is still shut down from just east of Denver here all the way to the Kansas border, 150 miles away. David? Wow, that's just incredible. Parts of I-70 still closed tonight. Let's go to ginger zee, timing this all out for us. Reporter: Hi, David. Such a critical night and a dangerous one, because on the southern side of that snow in Colorado, you have severe storms. A tornado watch from southern Missouri right into Louisiana. But let me time it out, because overnight tonight into tomorrow is when Minneapolis could pick up six to nine inches of snow. Chicago could see wind gusts up to 60 miles per hour. That will absolutely impact flights there. Then, on Thanksgiving day itself, it moves into the northeast. That could cause trouble. 20 to 40-mile-per-hour wind gusts could potentially effect the balloons. Some snow showers there. But how about that storm that's hitting tonight? This could bomb out, as we call it, drop 24 millibars in less than 24 hours. That means up to 80-mile-per-hour wind gusts, one to two inches of rain in California. We could see mudslides. This thing moves across the nation and that second storm could impact our weekend as everyone tries to get home. Right, following just about the same path right across the country. I know you'll be tracking that, ginger. And while we have you, you mentioned the potentially dangerous winds on Thanksgiving day. A lot of people wondering if the balloons for the famous parade could actually be grounded. Reporter: And we're also tracking that, David. Authorities telling us it is going to be a game-time decision on Thanksgiving day itself. They have thresholds, up to 34-mile-per-hour gusts and 23-mile-per-hour sustained winds. They'll fly the balloons if they are under that, but if they are at that or below, we've seen them ground the balloons where they take them and don't really fly them so high. That's an option. We haven't seen them not fly them since 1971. So, again, we'll see what they say on Thanksgiving day itself. David? All right, ginger, we just want everyone to be safe through the holiday. Ginger, we thank you for the warnings tonight.
This transcript has been automatically generated and may not be 100% accurate.